Perhaps you have the wrong bit. Also he is young to be trying to collect. You need to develop and muscle his back properly so that it can adequately support a rider. Sometimes horses have teeth problems, particularly four year olds as they have not yet lost all their baby teeth. Try getting an equine dentist to check his teeth.

Feet can also cause a horse to lift his head - usually this is a symptom of discomfort of some kind. Check that his saddle fits properly and is not pinching him somewhere.

I have started a blog on training horses. Go and have a look - I will be updating regularly with articles on training and related issues. Comments and questions are welcomed.

http://www.traininghorsesthenaturalway.blogspot.com